1. Field of the Invention
The present invention relates to a torque sensor abnormality detecting device which detects a torque on the basis of each inductance change of a pair of coils.
2. Description of the Related Art
In a torque sensor, since a coil itself has a temperature characteristic, the voltage based on each inductance of a pair of the coil changes depending on the temperature.
If an abnormality such as disconnection of the coil, disconnection of harness and contact failure is detected from each voltage, temperature compensation of each voltage is necessary because an influence of the temperature reaches each voltage, thereby disabling an accurate detection of the abnormality.
For this reason, a temperature sensor such as a thermister dedicated to detecting the temperature is provided on the torque sensor. Temperature compensation of each voltage is carried out based on a detected temperature to remove influence of the temperature and detect an abnormality such as disconnection.
The thermister needs to be provided on the torque sensor so as to detect the temperature thereof with an excellent sensibility for the temperature and therefore, a substrate or a holding component for holding the thermister is required, with the result that the quantity of required components increases leading to an increase of cost.
The present invention has been achieved in view of these problems. An object of the present invention is to provide a torque sensor abnormality detecting device capable of detecting an abnormality such as disconnection in the torque sensor or the like without the use of any temperature sensor so as to achieve low cost with fewer components.
According to the present invention, there is disclosed an abnormality detecting device of a torque sensor including a pair of coils in which inductance is changed in opposite directions corresponding to torque and a torque detecting means for outputting a torque detection voltage from both voltages based on a change in inductance of each of the pair of the coils. The abnormality detecting device comprises a pair of filter circuits for extracting DC component of each voltage based on the pair of the coils and change in each inductance, a differential means for outputting a difference in voltage of the DC voltage outputted from each of the filter circuits as the abnormality detection voltage, a memory means for memorizing a normal tolerance range preliminarily set up about the abnormality detection voltage of the differential means, and a determining means for determining whether or not the abnormality detecting voltage outputted by the differential means is in the normal tolerance range memorized by the memory means.